The present invention relates generally to a nucleic acid molecule which encodes a protein associated with the modulation of obesity, diabetes and metabolic energy levels. More particularly, the present invention is directed to a nucleic acid molecule and a recombinant and purified naturally occurring protein encoded thereby and their use in therapeutic and diagnostic protocols for conditions such as obesity, diabetes and energy imbalance. The subject nucleic acid molecule and protein and their derivatives, homologues, analogues and mimetics are proposed as therapeutic and diagnostic agents for obesity, diabetes and energy imbalance.
Throughout this specification, unless the context requires otherwise, the word xe2x80x9ccomprisexe2x80x9d, or variations such as xe2x80x9ccomprisesxe2x80x9d or xe2x80x9ccomprisingxe2x80x9d, will be understood to imply the inclusion of a stated element or integer or group of elements or integers but not the exclusion of any other element or integer or group of elements or integers.
Bibliographic details of the publications referred by author in this specification are collected at the end of the description. Sequence Identity Numbers (SEQ ID NOs.) for the nucleotide and amino acid sequences referred to in the specification are defined following the bibliography.
The increasing sophistication of recombinant DNA technology is greatly facilitating research and development in the medical, veterinary and allied human and animal health fields. This is particularly the case in the investigation of the genetic bases involved in the etiology of certain disease conditions. One particularly significant condition from the stand point of morbidity and mortality is obesity and its association with non-insulin-dependent diabetes mellitus (NIDDM) and cardiovascular disease.
Obesity is defined as a pathological excess of body fat and is the result of an imbalance between energy intake and energy expenditure for a sustained period of time. Obesity is the most common metabolic disease found in affluent societies. The prevalence of obesity in these nations is alarmingly high, ranging from 10% to upwards of 50% in some subpopulations (Bouchard, 1994). Of particular concern is the fact that the prevalence of obesity appears to be rising consistently in affluent societies and is now increasing rapidly in less prosperous nations as they become more affluent and/or adopt cultural practices from the more affluent countries (Zimmet, 1992).
In Australia, for example, studies using the definition of obesity of BMI greater than 30 have found prevalence rates for obesity of 8.2-9.3% in men and 9.1-11.1% in women (Risk Factor Prevalence Study Management Committee, 1990; Waters and Bennett 1995). The prevalence rates for obesity are increasing in Australia, as they are in many affluent societies. Bennett and Magnus (1994) found that the mean weight of Australian females aged 20-69 increased by 3.1 kg (from 61.7 to 64.8 kg) from 1980 to 1989, while the corresponding increase in males was 1.8 kg (from 77.0 to 78.8 kg). No change in height was observed during this period. Accordingly, the crude prevalence rates of obesity increased from 8.0 to 13.2% in females and from 9.3 to 11.5% in males (Bennett and Magnus 1994). All of the above changes were statistically significant (p less than 0.05).
The high and increasing prevalence of obesity has significant health implications. Obesity has been identified as a key risk indicator of preventable morbidity and mortality due to disease such as NIDDM and cardiovascular disease (National Health and Medical Research Council, 1996). The annual costs of obesity in Australia, for example, associated with these and other disease conditions have been conservatively estimated at AU$810 million (National Health and Medical Research Council, 1996).
A genetic basis for the etiology of obesity is indicated inter alia from studies in twins, adoption studies and population-based analyses which suggest that genetic effects account for 25-80% of the variation in body weight in the general population (Bouchard 1994; Kopelman et al, 1994; Ravussin, 1995). It is considered that genes determine the possible range of body weight in an individual and then the environment influences the point within this range where the individual is located at any given time (Bouchard, 1994).
Obesity is a complex and heterogeneous disorder and of considerable relevance to society. However, despite numerous studies into genes thought to be involved in the pathogenesis of obesity, there have been surprisingly few significant findings in this area. In addition, genome-wide scans in various population groups have not produced definitive evidence of the chromosomal regions having a major effect on obesity.
The hypothalamus has long been recognised as a key brain area in the regulation of energy intake. Early studies led to the dual-centre hypothesis which proposed that two opposing centres in the hypothalamus were responsible for the initiation and termination of eating, the lateral hypothalamus (LHA; xe2x80x9chunger centrexe2x80x9d) and ventromedial hypothalamus (VMH; xe2x80x9csatiety centrexe2x80x9d; Stellar 1954). The dual-centre hypothesis has been repeatedly modified to accommodate the increasing information about the roles played by various other brain regions, neurotransmitter systems, and hormonal and neural signals originating in the gut on the regulation of food intake. In addition to the LHA and VMH, the paraventricular nucleus (PVN) is now considered to have an important integrative function in the control of energy intake.
A large number of neurotransmitters have been investigated as possible hypothalamic regulators of feeding behaviour including neuropeptide Y (NPY), glucagon-like peptide 1 (GLP-1), melani-concentrating hormone (MCH), serotonin, cholecystokinin and galanin. Some of these neurotransmitters stimulate food intake, some act in an anorexigenic manner and some have diverse effects on energy intake depending on the site of administration. For example, gamma-aminobutyric acid (GABA) inhibits food intake when injected into the LHA, but stimulates eating when injected into the VMH or PVN (Leibowitz, 1985). Feeding behaviour is thought to be greatly influenced by the interaction of stimulatory and inhibitory signals in the hypothalamus.
In work leading up to the present invention, the inventors have made a significant break through in determining a genetic basis of obesity by identifying a genetic sequence differentially expressed in lean and obese animals. In accordance with the present invention, the inventors have isolated a novel gene which is proposed to be associated with energy balance and also in modulating obesity and diabetes.
One aspect of the present invention provides a nucleic acid molecule comprising a sequence of nucleotides encoding or complementary to a sequence encoding a protein or a derivative, homologue, analogue or mimetic thereof wherein said nucleic acid molecule is expressed in larger amounts in hypothalamus tissue of obese animals compared to lean animals.
Another aspect of the present invention is directed to a nucleic acid molecule comprising a nucleotide sequence, or a complementary form thereof, encoding an amino acid sequence substantially as set forth in SEQ ID NO:2 or SEQ ID NO:14 or an amino acid sequence having at least 30% similarity to all or a part thereof or a mimetic or said amino acid sequence or a nucleotide sequence capable of hybridizing to said nucleic acid molecule under low stringency conditions at 42xc2x0 C. and wherein said nucleic acid molecule is expressed in a larger amount in hyperthalamus tissue of obese animals compared to lean animals.
Yet another aspect of the present invention provides a nucleic acid molecule comprising a nucleotide sequence encoding or complementary to a sequence encoding a protein or a derivative, homologue, analogue or mimetic thereof wherein said nucleotide sequence is as substantially set forth in SEQ ID NO:1 or SEQ ID NO:13 or a nucleotide sequence having at least about 30% similarity to all or part of SEQ ID NO:1 or SEQ ID NO:13 and/or is capable of hybridizing to SEQ ID NO:1 or SEQ ID NO:13 under low stringency conditions at 42xc2x0 C. and wherein said nucleic acid molecule is expressed in a larger amount in hyperthalamus tissue of obese animals compared to lean animals.
Still yet another aspect of the present invention provides an isolated protein or a derivative, homologue, analogue or mimetic thereof which is produced in a larger amount in hyperthalamus tissue of obese animals compared to lean animals.
In yet another aspect of the present invention, there is provided an isolated protein or a derivative, homologue, analogue or mimetic thereof wherein said protein comprises an amino acid sequence substantially as set forth in SEQ ID NO:2 or SEQ ID NO:14 or an amino acid sequence having at least 30% similarity to all or part of SEQ ID NO:2 or SEQ ID NO:14 and wherein said protein is produced in a larger amount in hyperthalamus tissue of obese animals compared to lean animals.
A further aspect of the present invention is directed to an isolated protein or a derivative, homologue, analogue or mimetic thereof wherein said protein is encoded by a nucleotide sequence substantially as set forth in SEQ ID NO:1 or SEQ ID NO:13 or a nucleotide sequence having at least 60% similarity to all or part of SEQ ID NO:1 or SEQ ID NO:13 and/or is capable of hybridizing to SEQ ID NO:1 or SEQ ID NO:13 under low stringency conditions at 42xc2x0 C.
The protein of the present invention is referred to as xe2x80x9cbeaconxe2x80x9d and the nucleotide sequence encoding beacon is referred to as the beacon gene.
A further aspect of the present invention relates to a composition comprising beacon or its derivatives, homologues, analogues or mimetics or agonists or antagonists of beacon together with one or more pharmaceutically acceptable carriers and/or diluents.
Yet a further aspect of the present invention contemplates a method for treating a subject comprising administering to said subject a treatment effective amount of beacon or a derivative, homologue, analogue or mimetic thereof or a genetic sequence encoding same or an agonist or antagonist of beacon or beacon gene expression for a time and under conditions sufficient to effect treatment.
In accordance with this and other aspects of the present invention, treatments contemplated herein include but are not limited to obesity, anorexia, weight maintenance, energy imbalance and diabetes. Treatment may be by the administration of a pharmaceutical composition or genetic sequences via gene therapy. Treatment is contemplated for human subjects as well as animals such as animals important to livestock industry.
Still yet another aspect of the present invention is directed to a diagnostic agent for use in monitoring or diagnosing conditions such as but not limited to obesity, anorexia, weight maintenance, energy imbalance and/or diabetes, said diagnostic agent selected from an antibody to beacon or its derivatives, homologues, analogues or mimetics and a genetic sequence useful in PCR, hybridization, RFLP amongst other techniques.
A summary of SEQ ID NOs used throughout the subject specification is provided in Table 1.
A summary of the single and three letter abbreviations for amino acid residues used in the present specification is provided in Table 2.